U.S. patent number 4,488,125 [Application Number 06/395,368] was granted by the patent office on 1984-12-11 for coaxial cable structures and methods for manufacturing the same.
This patent grant is currently assigned to Brand-Rex Company. Invention is credited to Virgil T. Bolick, Jr., Kenneth W. Brownell, Jr., John M. Gentry.
United States Patent |
4,488,125 |
Gentry , et al. |
December 11, 1984 |
Coaxial cable structures and methods for manufacturing the same
Abstract
Novel discrete coaxial cable and coaxial cable assembly
constructions are disclosed. One preferred embodiment of the
invention is a flat coaxial cable assembly. The invention also
provides a novel method for manufacturing the coaxial elements
which are the primary structural components of the coaxial cables
and assemblies. In this method a signal wire and at least one drain
wire are embedded in a minor matrix of dielectric material. A
portion of the minor matrix material is peeled or skived away to
expose the drain wire or wires. The resulting product is then
wrapped in metal foil so that the foil makes electrical contact
with the exposed drain wires. This step yields a completed coaxial
element. A single element may be embedded in a major matrix of
dielectric to yield a coaxial cable or several elements may be so
embedded to yield a coaxial cable assembly.
Inventors: |
Gentry; John M. (Candler,
NC), Bolick, Jr.; Virgil T. (Asheville, NC), Brownell,
Jr.; Kenneth W. (Enka, NC) |
Assignee: |
Brand-Rex Company (Willimantic,
CT)
|
Family
ID: |
23562751 |
Appl.
No.: |
06/395,368 |
Filed: |
July 6, 1982 |
Current U.S.
Class: |
333/1; 174/115;
174/117F; 333/243 |
Current CPC
Class: |
H01B
7/0823 (20130101); H01B 11/1016 (20130101); H01B
13/016 (20130101); H01B 11/20 (20130101); H01B
11/1091 (20130101) |
Current International
Class: |
H01B
13/00 (20060101); H01B 11/18 (20060101); H01B
11/10 (20060101); H01B 7/08 (20060101); H01B
11/02 (20060101); H01B 13/016 (20060101); H01B
11/20 (20060101); H01P 003/06 () |
Field of
Search: |
;333/1,243
;174/115,117F |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1011416 |
|
May 1977 |
|
CA |
|
469043 |
|
Nov 1928 |
|
DE2 |
|
Other References
Electron Packaging and Production, May 1975, p. 28-Advertisement
for a coaxial ribbon Cable sold by AMP Incorporated. .
Amdahl Corporation, drawing No. B1044-000, showing a cable
structure..
|
Primary Examiner: Gensler; Paul L.
Attorney, Agent or Firm: Carter; David M. Stempel; Alan
Claims
We claim:
1. A coaxial cable comprising:
(a) a signal wire;
(b) at least one substantially straight drain wire spaced apart
from and parallel to said signal wire; said drain wire being in the
same plane with said signal wire for the entire length of said
cable;
(c) an elongated minor matrix of dielectric material, within which
said signal and drain wires are longitudinally embedded, said minor
matrix having an outer surface through which each of said drain
wires is partially exposed; substantially more of the surface of
each of said drain wires being embedded than being exposed;
(d) a conductive shield overlying said elongate minor matrix, in
electrical contact with substantially all of the surface of the
part of the exposed portion of each of said drain wires facing said
shield; and,
(e) a major matrix of dielectric material overlying said
shield.
2. The coaxial cable of claim 1 having a substantially flat
configuration.
3. The coaxial cable of claim 1 having a pair of drain wires.
4. The coaxial cable of claim 3, wherein said signal wire is
positioned between said two drain wires.
5. The coaxial cable of claim 4, wherein said signal and drain
wires are coplanar.
6. A coaxial cable assembly, comprising:
(a) a plurality of parallel spaced apart signal wires;
(b) at least one substantially straight drain wire associated with
each signal wire, each such drain wire being parallel to and spaced
apart from the signal wire with which it is associated along the
entire length of said cable;
(c) a plurality of elongate minor matrices of dielectric material,
each such minor matrix having longitudinally embedded therein one
of said signal wires and said drain wires associated therewith,
each such minor matrix having an outer surface through which each
of said drain wires is partially exposed; substantially more of the
surface of each of said drain wires being embedded than being
exposed;
(d) a plurality of conductive shields, each of which overlies one
of said elongate minor matrices, each such shield being in
electrically conductive contact with substantially all of the
surface of the part of the exposed portion of each of said drain
wires facing said shield; and
(e) a unitary major matrix of dielectric material overlying said
conductive shields.
7. A coaxial cable assembly according to claim 6, wherein said
minor matrices are positioned within said major matrix so that the
longitudinal axes of said minor matrices are substantially
parallel.
8. A coaxial cable assembly according to claim 6, wherein said
minor matrices are positioned within said major matrices so that
the longitudinal axes of said minor matrices are substantially
coplanar.
9. A coaxial cable assembly according to claim 6, wherein said
major matrix is substantially ribbonlike.
10. A coaxial cable assembly according to claim 6, wherein each
minor matrix has embedded therein a signal wire positioned between
a pair of parallel drain wires.
11. A coaxial assembly according to claim 6, wherein the
longitudinal axes of said signal and drain wires are parallel.
12. A coaxial assembly according to claim 6, wherein the
longitudinal axes of said signal wires are coplanar.
13. A coaxial assembly according to claim 6, wherein the
longitudinal axes of said drain wires are coplanar.
14. A coaxial assembly according to claim 6, wherein the
longitudinal axes of said signal and drain wires are located at
predetermined positions.
15. A coaxial assembly according to claim 6, wherein the
longitudinal axes of said signal and drain wires are coplanar and
parallel.
16. A coaxial assembly according to claim 15, wherein the
longitudinal axes of said signal and drain wires are located on a
predetermind center-to-center spacing.
17. A coaxial cable assembly including a plurality of coaxial
elements which are embedded in a supporting major matrix of
dielectric material, each of said coaxial elements comprising:
(a) a signal wire;
(b) at least one substantially straight drain wire spaced from and
parallel to said signal wire along the entire length of said
cable;
(c) an elongate minor matrix of dielectric material within which
said signal and drain wires are longitudinally embedded, said minor
matrix having an outer surface through which each of said drain
wires is partially exposed; substantially more of the surface of
each of said drain wires being embedded than being exposed; and
(d) a conductive shield overlying said elongate minor matrix in
electrically conductive contact with substantially all of the
surface of the part of the exposed portion of each of said drain
wires facing said shield, said major matrix overlying said
conductive shield.
18. A coaxial assembly according to claim 17, wherein said
plurality of coaxial elements are embedded in said supporting major
matrix so that the longitudinal axes thereof are parallel and
coplanar.
19. A coaxial assembly according to claim 18, wherein said assembly
is substantially flat.
20. A coaxial assembly according to claim 18, wherein the
longitudinal axes of said coaxial elements are located in said
supporting matrix at predetermined center-to-center spacings.
21. A coaxial assembly according to claim 18, wherein the
longitudinal axes of said signal and drain wires are substantially
parallel, coplanar and located on a predetermined pitch.
22. A coaxial assembly according to claim 18, wherein each coaxial
elements includes a pair of spaced-apart, parallel drain wires with
said signal wire being positioned therebetween.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrical cables. The invention
relates, more particularly, to a novel coaxial cable structure and
to flat coaxial cable assemblies comprising a plurality of such
coaxial cables, as well as methods for manufacturing the same.
2. Description of the Prior Art
Flat coaxial cable assemblies are well known in the prior art.
Generally, such cables include a spaced-apart, parallel and
coplanar array of parallel, insulated signal wires. The signal
wires are provided either with individual surrounding shield
conductors or with a single shield common to all of the signal
conductors. Usually, the shields consist of metal foil. In
addition, in order to facilitate termination of the shields with
electrical connectors, as well as the signal wires, it is usual to
provide one or more drain wires which are in intimate electrical
contact with the shield or shields. Thus, in cables wherein each
signal wire is provided with its own shield, there will usually be
a drain wire associated with each shield.
It has long been appreciated that in order to facilitate the
termination of flat cables, particularly mass or gang termination
of cables using automated installation tooling, it is necessary for
all of the conductors at a stripped cable end to be located at
predictable locations. This requirement is easily met in the case
of simple, non-coaxial, flat cable where one is faced simply with a
parallel, spaced array of wire conductors. In the case of flat,
coaxial cable having drain wires, however, it has proven difficult
to precisely locate both the signal and drain wires within the
cable.
For example, in some prior art cable assemblies, the drain wires
sprial around the associated signal wires. It is obvious that for
any randomly chosen cross section of such a cable, the precise
location of all of the drain wires cannot be predicted.
Accordingly, cables of this variety cannot easily be terminated,
except by hand.
In another type of flat, coaxial cable assembly, linear drain wires
are provided which occupy precisely specified locations within the
cable. Cable assemblies of this type are constructed by first
manufacturing the individual coaxial cables which make up the
assembly and then embedding the cables in a common dielectric
matrix. Each individual coaxial cable is made by placing an
insulated signal wire and an uninsulated drain wire in parallel
alignment and then wrapping the wire pair in a metal foil shield.
The completed coaxial cables are placed in the assembly in such a
way that all of the signal and drain wire pairs are similarly
oriented, thus making the location of each predictable. It will be
appreciated, however, that cable assemblies of this type are
difficult to manufacture because it is possible for the drain wire
in each coaxial cable to migrate underneath the foil shield, with
such migration being a particularly acute problem during the step
of foil wrapping itself. Of course, if a drain wire does move in
this way during manufacture, it will not occupy its assigned
location in the cable assembly.
In view of the foregoing description of the state of the art, it is
clear that there is a need for a flat, flexible, coaxial cable
assembly in which all conductors are located at predictable
locations, in order to facilitate termination, and which may be
easily and simply manufactured.
The objects of the present invention, are, accordingly, to provide
such a cable assembly, as well as methods for manufacturing the
same.
SUMMARY OF THE INVENTION
The present invention satisfies the above-stated objects by
providing a flat, coaxial cable assembly in which all of the
conductors occupy predictable locations. The assembly, which is
easily manufactured, comprises a plurality of individual coaxial
cables which are embedded in a flat, elongate, supporting major
matrix of dielectric material. Each of the individual coaxial
cables comprise a signal wire and at least one drain wire which is
spaced from and parallel to the signal wire. The signal and drain
wires are longitudinally embedded in an elongate minor matrix of
dielectric material in such a way that the drain wires are
partially exposed through the outer surface of the minor matrix. A
conductive shield overlies the elongate minor matrix and makes
electrical contact with the partially exposed drain wires.
The individual coaxial cable elements of this novel assembly may be
manufactured by positioning at least one drain wire in
spaced-apart, parallel relationship to a signal wire and then
embedding the signal and drain wires in a dielectric material. A
portion of the outer surface of the dielectric matrix is
selectively removed in order to partially expose the drain wires.
Then, the cable is overlaid with a shield of conductive material in
such a way that the shield makes electrically conductive contact
with the partially exposed drain wires.
To fabricate the finished flat, coaxial cable assembly, a plurality
of individual cable elements are positioned in a spaced-apart,
parallel, coplanar array and then embedded in a major matrix of
dielectric.
In addition to the foregoing, it is, of course, within the scope of
the invention to produce coaxial cables, rather than coaxial cable
assemblies, by overlaying a lone coaxial cable element, produced as
described above, with an outer sheath of dielectric material.
Additionally, it is within the scope of the invention to produce
coaxial cable assemblies having non-planar configurations, should
this be desired.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of one embodiment of a flat,
coaxial cable assembly according to the invention.
FIG. 2 is a cross-sectional view of a modification of the cable
assembly depicted in FIG. 1.
FIG. 3 illustrates one embodiment of a coaxial element according to
the invention during a stage of its manufacture.
FIG. 4 is a cross-sectional view of a completed coaxial element
according to the invention.
FIG. 5 is a diagramatic view, from the top, depicting a method for
manufacturing flat, coaxial cable assemblies according to the
invention.
FIG. 6 is a diagramatic view, from the side, which further depicts
the method shown in FIG. 5.
FIG. 7 is a cross-section view of one embodiment of an individual
coaxial cable according to the invention.
FIG. 8 is a cross-sectional view of a still further embodiment of a
flat, coaxial cable assembly according to the invention.
FIG. 9 illustrates a further embodiment of a coaxial element
according to the invention during a state of its manufacture.
FIG. 10 illustrates, in cross-section, another embodiment of a
coaxial element according to the invention.
FIG. 11 is a cross-sectional view of a further embodiment of an
individual coaxial cable according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to the drawings in detail, FIG. 1 is a cross-sectional
view illustrating one embodiment of a flat, coaxial cable assembly
according to the invention. The assembly 10 comprises a pair of
coaxial elements 12A and 12B (or simply 12 when referred to
generally) which are embedded in a supporting major matrix 14 of
dielectric material, PVC, for example. Each of the coaxial elements
12 comprises a signal wire 16 and a pair of drain wires 18, which
are spaced from and parallel to the signal wire. The signal and
drain wires are longitudinally embedded in an elongate minor matrix
20 of dielectric material, which may also be PVC, for example. Very
importantly, while the drain wires 18 are immobilized by the minor
matrix in which they are embedded, they are partially exposed
through the outer surface of the minor matrix. In this way, the
drain wires are able to be placed in electrically conductive
contact with a conductive shield 22, which overlies the elongate
minor matrix 20. The shield 22 is preferably composed of metal
foil.
While the coaxial cable assembly 10 comprises only two coaxial
elements, it will be appreciated that as many additional coaxial
elements may be provided as desired. Further, the spacing or pitch
of the wires within the assembly can be modified to meet specific
requirements. For example, while the pitch y between drain wires in
neighboring coaxial elements is shown as being greater than the
pitch x between the signal and drain wires within an element, the
coaxial elements could be moved closer together in order to make
the pitch between all of the wires uniform.
FIG. 2 illustrates a possible modification of the coaxial cable
assembly depicted in FIG. 1. The assembly 24 is identical to the
assembly 10, except that in the coaxial elements 13A and 13B the
signal wires 26, which are of a smaller gauge than the signal wires
16, are overlayed with insulation 28. The insulation 28, which is
of a different composition than the dielectric 20, can serve two
purposes. First by proper selection of material and dimension, the
insulation 28 can be employed to finely adjust the dielectric
constant of the insulation surrounding the signal wire, which by
implication also finely adjusts the impedance of the coaxial
element. Second, if the insulation 28 is comprised of a material
which does not adhere to the insulation 20, it is possible to strip
the end of the cable assembly in such a way that the drain wires
are fully exposed but the signal wires retain their insulation
sheaths 28. For example, the insulation 28 might be polyethylene
and the insulation 20 PVC. In this modification of the cable
assembly, the signal wires 26 are of reduced gauge both in order to
make room for the insulation 28 and in order to reduce cable
impedance.
FIG. 8, which is a cross-sectional view of a coaxial cable assembly
30, illustrates another embodiment of the invention. Here again, a
plurality of coaxial elements 32A through 32E (or simple 32 when
referred to generally), are longitudinally embedded in a major
matrix of dielectric material 34. Each coaxial element 32 is
similar to the elements 12 of FIG. 1, including an outer conductive
shield 36, a minor dielectric matrix 38, a signal wire 40, and a
drain wire 42. FIG. 8 is intended to show that a single drain wire
may be employed for the purpose of terminating the shield 36 just
as advantageously as the pair of drain wires 18 depicted in FIG. 1.
Indeed, the number of drain wires employed is not critical and will
be dictated mainly by the design of the connector to be used for
terminating the cable assembly. Further, the cross-sectional
geometry of the coaxial elements is also to a large extent not
critical, and circular elements 32 may be used rather than
rectangular elements 12, it being recognized that element impedance
will be governed somewhat by the element's geometry.
While the invention finds its greatest utility in the provision of
novel coaxial cable assemblies, it will be appreciated that novel
discrete coaxial cable structures are within the scope of the
invention as well. For example, as shown in FIGS. 4 and 7, a
discrete coaxial cable 44 may be fabricated which comprises a
single coaxial element 12, which is surrounded by a major matrix of
insulation 46. Similarly, as shown in FIGS. 10 and 11, a coaxial
cable 48 can be fabricated by overlaying a coaxial element 32 with
a layer of dielectric 50.
The novel coaxial cables and coaxial cable assemblies provided by
the invention are relatively simple and economical to manufacture.
FIGS. 5 and 6 depict, schematically, a method for producing flat
coaxial cable assemblies such as the assembly 10 shown in FIG.
1.
Each of the coaxial elements 12A and 12B are prepared in the
following manner. A pair of drain wires 18 and a signal wire 16 are
fed, in spaced-apart, parallel and coplanar alignment, to a first
extruder 50, where they pass through a pressurized reservoir of
dielectric material 52. The wire set emerges from the extruder
embedded in a minor matrix of dielectric material 20 which is
solidified by passage through a water bath 54.
The coaxial element precursor next passes through a blade set 56
which removes portions of the minor matrix 20 so that the drain
wires are partially exposed through the new outer surface of the
matrix, as best shown in FIG. 3. It has been found to be preferable
to extrude the minor matrix 20 in such a way that it comprises a
main portion and protuberant selvage portions 58 which are
separable from the main portion, with each of the drain wires 18
being partially embedded in the main portion and partially in a
selvage portion, as shown in FIG. 3. It has been found that the
constricted transition zones 60 between the main and selvage
portions of the minor matrix assist in guiding the blades 56. In
addition, those skilled in the art will recognize that with the
proper selection of dielectric material, it would be possible to
peel off the selvage portions 58, eliminating the requirement for
the blades 56.
The as yet incomplete coaxial element next passes through a furling
block 62 where a metal foil tape 64 is applied around the minor
matrix 20 to form the conductive shield 22. The foil tape 64 is
pressed into electrically conductive contact with the partially
exposed drain wires 18 by the furler 62. It should be noted that,
in contrast to prior art coaxial cable forming methods, the drain
wires are at this point held immobile by the minor matrix 20. In
this way, migration of the drain wires during the foil furling step
is eliminated, assuring that the various wires in the finished
coaxial cable assembly will occupy precisely their preassigned
locations. Cable assemblies manufactured in this fashion are thus
easily mass or gang terminated using automated installation
tooling.
The now complete coaxial elements 12A and 12B are next drawn into
an extruder 66 which includes a reservoir of pressurized
thermoplastic resin 68. The elements emerge from the extruder
embedded in a ribbonlike major matrix 14 of the thermoplastic
resin. After cooling in a water bath 70, the manufacture of the
coaxial cable assembly 10 is complete.
The manufacture of a coaxial cable assembly such as 30 of FIG. 8 is
accomplished in much the same fashion as that just described for
the assembly 10. Of course, in this instance the coaxial element
precursor which emerges from the initial set of extruders is
configured as shown in FIG. 9. A single protuberant selvage portion
72 is separated from the main portion of the minor matrix 38 by a
knife 74 to partially expose a lone drain wire 42 which is embedded
in the matrix. Next metal foil is applied in order to form the
coaxial element 32 shown in FIG. 10. A desired number of coaxial
elements 32 are then fed into an extruder where they are embedded
in a major matrix of dielectric material 34 to yield, after
cooling, the finished coaxial cable assembly.
While there have been shown and described only several embodiments
of the invention, changes and modifications in construction and
method will now be obvious to those skilled in the art which do not
depart from the scope of the invention. It is intended by the
appended claims to cover all such changes and modifications.
* * * * *